1. Field of the Invention
The present invention relates to an ink jet head for recording data in a recording medium by discharging a liquid (also referred to as ink) to the recording medium, a head holder to which a flexible cable joined to the ink jet head is set, a head assembly configured by setting the ink jet head and the flexible cable to the head holder, a head cartridge configured by removably setting a tank holder for mounting an ink tank to the head assembly, an ink jet recorder mounting the head cartridge, and a method for manufacturing the head assembly.
The present invention is an invention which can be applied to an apparatus such as a printer, a copying machine, a facsimile having a communication system, or a word processor having a printer which record data in a recording medium such as paper, yarn, cloth, leather, metal, plastic, glass, wood, or ceramics and moreover, applied to an industrial recorder configured by complexly combining the present invention with various processors. In this case, "recording" in the present invention represents providing not only a meaningful image such as a character or graphic but also a meaningless image such as a pattern for a recording medium.
2. Related Background Art
A flexible cable serving as a driving wiring for an ink jet head has been frequently used for ink jet recorders so far. The flexible cable is flexible for deformation of the shape of the cable and also versatile for bending of the cable, it is effective as wiring means extending from the ink jet head to the connector section of the ink jet recorder. In the case of an ink jet recorder, a head assembly is configured by setting an ink jet head and a flexible cable connected to the ink jet head to a head holder. A contact portion to which an electric signal for discharging ink from the ink jet head is formed on the flexible cable. When setting a head assembly to, for example, the carriage of the ink jet recorder, the contact portion of the flexible cable of the head assembly is brought into contact with and electrically connected with the contact portion of the ink jet recorder.
For example, only a flexible cable may be set to a head holder to which an ink jet head will be set. In this case, the flexible cable has versatility. However, when setting an assembly configured of the ink jet head and the flexible cable to the head holder, the flexible cable is set to the head holder by winding the flexible cable on the outside face of the head holder. In this case, the entire flexible cable is exposed to the outside of the head holder.
However, to set an assembly configured of a flexible cable and an ink jet head to a head holder in accordance with the conventional manner, if a head assembly is configured so that the entire flexible cable is exposed to the outside of the head holder as described above, problems occur that the number of restrictions for setting the flexible cable increases and the fabrication cost increases.
Moreover, a head assembly having an ink jet head and a flexible cable is generally removably mounted on an ink jet recorder. For the head assembly removable from the ink jet recorder, a flexible cable on which a contact portion serving as an electric contact with the ink jet recorder is formed is important.
When a head assembly having an ink jet head is removably set to an ink jet recorder, a flexible cable exposed to the outside of a head holder may receive an impact when the head assembly is set, removed, or operated and be disconnected or damaged. Thus, when the flexible cable is damaged, recording may be interrupted and it may be impossible to use the head assembly.
TAB (Tape Automated Bonding) and FPC (Flexible Printed Circuit) are used for the above flexible cable or a technical configuration similar to the flexible cable. In the case of a configuration for using the TAB and FPC for a recorder, by fixing them to an ink jet head and connecting them to a contact portion provided for the carriage of the recorder, a signal and electric energy supplied from the recorder for driving an electrothermal element for generating energy used to discharge ink as droplets are supplied to the electrothermal element. For example, when using the TAB, it is permitted to directly connect the TAB to the pad of a board on which an electrothermal element is formed. When using the FPC, it is permitted to connect the FPC to the pad through a PWB (Printed Wiring Board).
A hot-melt sheet using ethyl vinyl acetate (EVA) or ethylacrylic acid (EAA) as a base polymer has been used so far in order to bond an electric circuit component to a structural member. The hot-melt sheet has advantages that it can be bonded at a relatively low temperature, it is unnecessary to dry the sheet in the bonding step because it does not contain a solvent or water, and the productivity is improved. Moreover, it is possible to easily automate the bonding step and simplify maintenance.
However, urea is frequently added to ink used for an ink jet head in order to prevent the ink from sticking to an ink discharge port. Hydrolysis of EVA or EAA is progressed due to ammonia gas or alkali vapor produced due to decomposition of the urea and thereby, an adhesive strength may be extremely lowered.
Moreover, the number of discharge ports formed on one ink jet head tends to increase more and more for high-speed printing. Therefore, the thickness and width of the copper foil of TAB or FPC tends to increase in order to flow a large current. As a result, unless the rigidity of a flexible wiring board is improved and bonded to a structural member at a higher adhesive strength, the adhesive strength is defeated by the reaction of TAB or FPC and a trouble such as positional shift or separation from the structural board may occur.
Moreover, a package may be exposed to a high temperature of 60.degree. C. when a recorder circulates. Therefore, it is also necessary to consider the adhesive strength at a high temperature. EVA or EAA has a large adhesive strength at 25.degree. C. but a relatively small adhesive strength at a high temperature. As a result, the adhesive strength is defeated by the reaction of TAB, FPC or the like, and a trouble such as positional shift or separation may occur.